The present invention relates to a voltage regulator for use with a polyphase magneto generator and in combination with a rectifier circuit provided to rectify the output of the generator to charge a battery, and more particularly to a voltage regulator having thyristors adapted to short-circuit the output of the generator when the battery terminal voltage is excessive.
A prior art voltage regulator of the above mentioned type employs a plurality of the thyristors for short-circuiting the output of a generator. A voltage sensing device is provided to detect the voltage of the battery and to trigger an auxiliary thyristor when the battery terminal voltage is excessive. The auxiliary thyristor itself is provided to trigger one of the main thyristors for short-circuiting the output of the winding of the generator having the phase in advance of any of the remaining windings associated with the remaining thyristors. Each of the remaining thyristors are provided to be triggered by a voltage drop across a resistor or a diode connected in series with one of other thyristors for short-circuiting the output of the windings in advance of the winding associated with the thyristor to be triggered. Since large short-circuiting currents flow through the resistors or the diodes in series with the main thyristors, they need to have large capacity, and are therefore large in volume and expensive.